Continuous grignard reaction process



Jan. 2,1, 1947. cfa. ARNTzr-:N l 2,414,505 vCOHTINUQUS GRIGNARD REACTION PROCESS y Y A Filed sept. 15, 1945 @Sheets-sheet 2 w|TNEssEs= v INVENTOR` Patented Jan. 21, 1947 coN'rINUoUs s PATENT OFFICE GRIGNARD REACTION PROCESS Clyde E. Arntzenwilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvanial Application September 15, 1943, Serial No. 502,451

f 1 This invention relates to the apparatus and a method of preparation of chemical products wherein an organometallic compound, such as a Grignard reagent, is employed. I

A variety of chemical reactions have been carried out by the, use of Grignard reagents which are solutions of organomagnesium compounds. The Grignard reagent is an extremely convenient and controllable reagent by means of which or-v ganic compounds may be synthesized. Particularly for laboratory work the use of a Grignard reagent permits the ready and convenient preparation of a great variety of organic compounds.-

Heretofora the application of Grignard reagents to relatively large scale production has been attended with certain dilllculties. The reagent was usually prepared separately in a rela- 3 Claims. (Cl. 26o-684) tively large quantity of ether. The use of such large quantities of ether is inconvenient and dangerous4 as a lire hazard. A further difficulty is met in that the concentrationl of the organomagnesium compound in the ether frequently dctermines which one of several possible reactions would be-favored. Other disadvantages such as length of time to complete a'total reaction and the like are known to those skilled in the art.

The object of this invention is to provide for substantially continuously producing and supplying a predetermined concentration of Grignard reagent in a solvent to a vessel in which a reaction involving the reagent occurs.

Another object of the invention is apparatus for conducting predetermined complementary chemical reactions in which a Grignard reagent is produced in one portionof the apparatus as an ether solution of predetermined concentration and circulated to another portion in which a. second chemical reaction takes place and the ether recovered and recirculated to the initial Grignard reaction whereby relatively small amounts of ether are required.

l A still further object of the invention is to provide for introducing a predetermined concentration of Grignard reagent in ether substantially continuously to take part in a. primary chemical 4 reaction involving the Grignard reagent to provide for a predetermined type of product.

Other objects ofthe invention will, in part, be obvious, and will, in part, appear hereinafter. For a. fuller understanding of the nature and objects of the invention, reference shouldbe had tol the following detailed drawings, yin which:

Figure 1 .is a schematic view in elevation partly in section of one form of apparatus 'according to' the invention, and

Fig. 2 is a plan ln elevation partly in section to provide an showing schematically a second form of the invention.

Referring to Fig. 1 of the drawings, there is illustrated an apparatus in which organic halides in gaseous form may be employed in carrying out reactions involving the preparation and use of the Grignard reagent. The apparatus is particularly suited for producing organometallic compounds, such as organosilicon alkoxides. Such compounds may be prepared in the apparatus by reacting an organic silicate, for example, ethyl silicate, with a Grignard reagent to substitute an alkyl group for an alkoxide group. There are four possible reaction products that may be produced from ethyl silicate by this reaction. The

substitution of a methyl group may be so carried out that a monomethylsilicon triethoxide, a dimethylsilicon diethoxide, atrimethylsilicon monoethoxide or tetramethylsilicon may be produced. The reaction is indicated in the following equations:

onlsi(oc,H,),+Mg(oC,H.)Br

Forl purposes of preparing resins therefrom, the trimethylsilicon ethoxide and tetramethylsilicon are deemed undesirable. The monomethyl and dimethylsilicon ethoxides may be treated to produce highly desirable resinous materials and therefore the reaction favoring their production is preferred. It has been found that dilute s olutions of methylmagnesium halide in ether favor the formation of the monomethyl and dimethyl forms of the product.

The apparatus of Fig. 1 permits the convenient and economical preparation of dilute solutions of methylmagnesium halide in ether. The problem of storing large volumes of an ether solutionof a Grignard reagent and thetedious fractional distillation of the ether from the products is avoided by use of the-apparatus.

The Grignard reagent is prepared in a first reaction vessel I2 disposed in a receptacle -Il containing a mixture I6 of ice and water in order `to absorb the heat of reaction and to facilitate' cous lubricant between. y

An organic ether such as ethyl ether to act applied to seal the space thereas the solvent for the reaction product is introduced through the side neck 26 and the side neck 80 of the vessell2 from sources to be set forth in detail. The organic halide taking part in producing the Grignardv reagent enters through a second side neck 30. Magnesium metal particles are introduced as a mass into the reaction-vessel I2 at the start of. the operation.

Means may be. provided if desired for introducing magnesium particles from a container to the ves-,

sel I2 through a wide mouth valve (not shown) i i which may be operated at stated intervals to admit a small amount of magnesium metal Without permitting gas to escape.

A gaseous organic halide, such, for example, as methyl bromide, is contained in a tank 32 and the amount of the methyl bromide introduced to the apparatus is determined by the setting of valve 34. Methyl bromide gas passes from the The reaction vessel 90 is disposed within a heater 92- which is electrically operated by current supplied by the conductor 94. Other means of heating the reaction vessel 90 may be 4employed, for example, an immersion heater may be introduced. into the vessel 90 or some other` convenient heating device employed.

In order to determine the temperature in the reaction vessel 90, a thermometer 98 is admitted through the neck 96. A,thermocoup1e or the tank 32 into'tlie line 36 which has a connection 4 through a branch conduit 38 into a .safety pressure regu1ator'40 containing a po'ol of mercury 42 into which the lower end of a tube 46 extends. The line 36 is connected by a branch line to an acid trap 50 to catch any acid backing up from a cleaning trap disposed further on in the line.

In order to purify the methyl bromide gas of Water vapor or other deleterious matter, the conduit 5 4 is directed into the acid cleaning bottle 58 containing sulphuricacid 60. An extension to boil at a given`- temperature.

ofconduit 54 dips below the surface of the sulphuric acid 60 whereby the-methyl bromide gas is bubbled through the acid. A pinch clamp 56 is provided on conduit 54 tolshut off gas from flowing to the acid immersed conduit 62 in case the apparatus is not in use. Acid Washed gas is collected in dome 64 of bottle 58 and conveyed by tube 66to a calcium chloride absorption flask 68. The gas is introduced at the bottom of the flask`68 from where it passes through a, body of granular calcium chloride I0 to the line 12 connecting to the neck of vessel I2. Other means of purifying the organic halide may also be used.

A supply of ether for make-up purposes and the like is contained in the ask 'I6 from which its ilow to neck 80 of vessel I2 is controlled by the valve 18. In order tomaintain an equilibrium gas pressure at both faces of the ether in the flask 'I6 when the valve 'I8 is opened and exequivalent may be substituted for` the thermometer. The contents of the vessel 90 are main-- `tained in a state of agitation vby the stirrer |00 perature of the ether.

operated by the motor |02 through the sealing gland |04.

The temperature of the ingredients in the reaction vessel 90 is maintained at the boiling tem- The 'rate of input of the heat is so adjusted as tocause the ether to distil through tube |I0 and pass as condensate into flask .I2 at a rate corresponding to ethei flow through outlet 82 to ask 90.

'Ille ether vapors rise up neck 84 to a portion |08 of enlarged diameter containing a quantity 'of glass beads and the like to function as a trap for particles of entrained liquid and for condensing vapor of material with a boiling point above the boiling point of the ether. Liquid particles caught on the beads |08 and condensed vapors trickle back slowly into the vessel 90. The

' liquid-free ether vapors pass upwardly through the tube |I0 to a condenser I I2 in which they are exposed to an extensive cooled surface I I4 maintained at'such a temperature as to cause liquefaction of the ether. A cold water inlet II6 providesfor a flow of lcold water within the condenser against the face of surface ||4 opposite to that contacted by the ether vapors. The warmed water is removedv through the outlet |I8. The

. liquid ether condensedin the condenser ||2 posed to the pressure in vessel I2, a bypass 14 is connected from the'line l2 to the upper partof the ilask 16.

To start the reactions, the rst reaction vessel I2`is partially lled with magnesium metal, then ether is admitted fromlthe flask 16 to a predetermined initial amount. 'and thereafter the stirrer I 8 is set in motion. Into the second reaction vessel 80 is introduced Aa predetermined quantity of the reactant, ethyl silicate in this example, with enough ether to cause the'mixture Valve 34 from the tank of organic halide is cracked open to admit the halide gas vat a predetermined rate of flow through the sulphuric acid 60 and the calcium chloride I0 into the reaction vessel I2.

The reaction of the magnesium metal and the organic halide in the ether produces the socalled Grignard reagent. The addition of the I i various reactants gradually fills the reaction vessel I2 and thelevel of the ether solution therein trickles at a predetermined rate through the neck 26 back into the reaction vessel I2 for producing further Grignard reagent.

As a pressure regulator for the methyl bromide gas, a tube |20 is connected to the condenser ||2 and leads to a regulator |24. The pressure regulator contains a tube |22 connected to the tube |20 and leading a predetermined distance below the surface of a pool of mercury |26. The escape of bubblesat relatively long intervals assures the presence of the desired gas pressure. In case the gas pressure exceeds the pressure equivalent of the mercury |26 as determined by the depth of immersion of tube |22 below thesur'face thereof,

the vaporsiescapeto the atmosphere through the Y outlet |28.

When-'theapparatus of Fig. 1 isto be initially employed, it must be purged of air in order to avoid the oxidationof the Grignard reagentor t an ether vapor explosion. In such case, the pinch clamp |32 is opened and the ether vapors and methyl bromide are permitted to displace the air in the apparatus. The air passes through tube I20'and then through line |30 through chamber |34 containing a supply of a dessicant |86, such as calcium chloride, and through the outlet |38. The calcium chloride is present mainly to prevent admission of moisture to the apparatus in case the internal pressure of the apparatus falls below atmospheric air pressure when valve |32 is open. n

It will be obvious that a relatively small initial quantity of ether will be satisfactory for continuously producing a predetermined output of Grignard reagent in the rst reaction vessel I2 and for conveying the reagent to the second reaction vessel 90 whereby the desired composition is produced. The small amount of ether is continually recirculated to act as solvent for more Grignard reagent. By admitting more ether from the storage flask 16, the boiling point of the mixture in vessel 90 may be lowered.

In some cases it may be desirable to employ liquid organic halides instead of the gaseous halide employed in the Fig. 1 modicaton of the through the outlet :se tu the atmosphere. The

function or the calcium ,chloride` is to prevent moisture being admitted in' case the apparatus is accidentally maintained lbelow atmospheric pressure. Within the tube 256 is,disposed a smaller inlet 288 for introducing a liquid organic halide entering by means of the inlet 280'.

apparatus. Referring to Fig. 2 of the drawings,

there is illustrated a modified form ofthe invention comprising an apparatus in which the reactions may be carried out employing a liquid organic halide. The apparatus of Fig. 2 is composed of a nrst reaction vessel 202 for preparing the Grignard reagent, the vessel being disposed in a pan' 204 containing an ice and water mixture 206` to maintain a low temperature. A stirrer 208 for agitating the contents in the reaction vessel 202 is operated by the motor 2|0 through the gland 2|2 passing through the neck 2|4 of the vessel. The organic halide and condensed. ether are admitted to the vessel 202 through a side neck 2|6. The Grignard reagent produced from the reaction of the magnesium metal and liquid organic halide in ether rises within the reaction vessel 202 through the filter plug of vglass wool, or the like, 222 to the outlet 220. The Grignard reaction iioWs through'` the outlet 220 into neck 224 of the reaction vessel 226 where the main reaction takes place. 4 I

The second reaction vessel 226 is heated to a temperature above the boiling point of the ether by the heating means 228 operated by an electrical' current flowing through the conductor 230. The temperature of the vessel contents may be. determined by the thermometer 234 passing through the neck 232 of the vessel. Stirring of the contentsof the vessel is effected by the stirrer 236'operated by the motor 238 passing through sealing gland 240.

Ether vapors produced by the heating of the flask 226 rise through the neck 224 to a fractionation column 242 containing glass beads or other equivalent material 244 to trap liquid parl ticlesand to condense high boiling point liquid vapors. An inverted-U -neck 246 conveys the liquid-free vapors to the condenser 248.

Within the condenser 248 `is disposed an extended cooled surface 250 maintained at a temperature sufficient to cause ether vapors to con- `dense by theaiiow of cooling water or the like 'through an inlet 252 and vented through an outlet 254. Liquid ether produced by condensation trickles through the neck 2|`6 back to the reaction vessel 202 to act as a solvent in the further production of Grignard reagent.

Connected to the top of the condenser is a tube 256 which permits the purging of air from the apparatus when being initially employed at which time the mixture is vented through the tube 258 and passed through the chamber 262 containing a desiccant 264, such as calcium chloride, and

Undersome conditions, the neck 2|8 of the vessel 202 will ll with Grignard reagent solution and siphon in a steady stream through the outlet '220, To prevent this from occurring, the neck 282 is connected to the neck 2|8 by a bypass 284 which breaks the vacuum apparently caused by the condensation of ether in the neck.

In case additional ether requires to be added to the vessel 202, the flask 286 providedy with valve 288 'is connected tothe bypass 284. A moisture absorbing air admitting trap 290 is connected to the iiask 286 to permit air to enter as ether is withdrawn.

It willbe apparent of either Fig. 1 or Fig. 2 is to be employed on a large scale, the several vessels wherein the r`eactions take place may be in the form of large auvtoclaves or the like with suitable changes in the various pipes and other fixtures to permit a more suitable control of the flow and passage of the several ingredients. Where calcium chloride has been indicated as a moisture absorbent, other dehydrating agents may be made use ,of with sub` stantially similar results, for instance, anhydrous calcium sulphate or the like may be substituted.Y The cooling Amixture to ensure a satisfactory Grignard reagent reaction may be other refrigerants than ice and water as indicated above. As mentioned previously, magnesium metal may be added from a source of supply by equipping the supply device with a large aperture valve or a metering member to permit particles to flow l.

therethrough into the Grignard reagent vessel.

Solid organic halides dissolved in a minimum amount of the ether may also be employed in the form of the apparatus of Fig. 2 described'for use with liquid organic halides.

Other metals, such as lithium, which readily I form reactive organometallic compounds with or' ganic halides may also be used instead of magnesium.

Since certain changes may be made in the apparatus above described and different embodiments of the invention could be made without departing from the spirit thereof, it is intended that all matter contained in the abovedescription be considered as illustrative and not in a limiting` sense. I claim as my invention:

1. In the process of preparing a reaction product over a period of time involving the use of a solution of' a Grignard reagent in an ether which comprises applying to magnesium metal in a first zone substantially continuously during -the reaction period an organic halide and ether to produce the solution of Grignard reagent in the ether, withdrawing substantially continuously throughout the reaction period the solution of that lwhen the apparatus 7 4 Y Grignard reagent from said rst zone and conveying the solution to a second zone containing a substance which reacts with the Grignard reagent to form a relatively non-volatile product, distilling o the ether substantially continuously from the second zone, condensing the ether va- 2,414,sos

the condensed liquid ether and additional organic halide admixed in the ether to said rst zone to pors, and substantially continuously conveying the condensed liquid ether to said iirst zone to prepare additional solution of Grignard reagent,

` whereby the ether is recirculated and a relatively small amount is employed.

solution of a Grignard reagent in an ether which comprises applying to magnesium metal in a rst zone substantially continuously during the reaction period an organic halide and ether to produce the solution of Grignard reagent in the ether, withdrawing substantially continuously throughout the reaction period the solution of y Grignard reagent from said first zone and conveying the solution to a second zone containing a substance which reacts with the Grignard reagent to form a relatively non-volatile product, distilling oil' the ether substantially continuously from the second zone, condensing the ether vapors, and'substantially continuously conveying v 2. In the process of preparing a reaction product over a period of time involvingthe use of a prepare additional solution of Grignard reagent, whereby the ether is recirculated and a relatively small amount is employed. v

3. In the process of vpreparing a reaction product over a period of time involving thev use of a solution of a Grignard reagent in an ether which comprises applying to ametal capable of forming Grignard reagent in a. irst zone substantially y continuously during the reaction period an organic halide and ether to produce the solution of Grignard reagent in the ether, .withdrawing substantially continuously throughoutthe reaction period the iolution olf` Grignard reagent from said first zone and conveying the solution to a second zone containing a substance which reacts with the Grignard reagent to form a relatively nonvolatile product, distilling otr the ether substantially continuously from the second zone, condensing the ether vapors',`and Substantially continuously conveying the condensed liquid etherto -said first zone to prepare "additional solution of Grignard reagent, whereby the ether is recirculated and a relatively small amount is employed.

CLYDE E ARNTZEN. 

